Oil atomizing burner using low pressure air



June 7, 1966 R. E. SCHRETER ETAL 3,254,846

OIL ATOMIZING BURNER USING LOW PRESSURE AIR Original Filed Dec. 20, 1962 2 ts- 1 INVENTORJ 064??? 6- 666095727? fiEAW/v I PAR/r5? June 1966 R. E. SCHRETER ETAL 3,254,846

OIL ATOMIZING BURNER USING LOW PRESSURE AIR Original Filed Dec. 20, 1962 2 Sheets-Sheet 2 FIG 5 52 FIG. /0

ATTORNEYS 3,254,846 OIL ATQMIZING BURNER USING LOW PRESSURE AIR Robert E. Schreter, Lebanon, and Melvin J. Parker, Palmyra, Pa., assignors to Hauck Manufacturing Company, Lebanon, Pa., a corporation of New York Continuation of application Ser. No. 246,186, Dec. 20,

1962. This application Jan. 21, 1965, Ser. No. 428,601

10 Claims. (Cl. 239-400) v This application is a continuation of an earlier application Serial No. 246,186, filed December 20, 1962, now abandoned. The invention relates to oil burners, and more particularly to an oil atomizing burner using low pressure air as the atomizing agent.

The primary object of the invention is to generally improve oil burners. A more particular object is to increase atomizing efiiciency, thus requiring less atomizing air. The improvements arevaluable regardless of burner size and use, but are especially valuable in oil burners of large size, used for example in combination with a large rotating cylinder or a kiln. for industrial purposes such as the drying of sand or gravel, the heating of asphalt, or the manufacture of cement.

Another object of the invention is to provide such burners requiring the use of only low pressure air, which may be provided in large quantities at low cost.

Still further objects are to provide a burner which may be used with a variety of fuel oils; which efiiciently atomizes the oil; which has good directional properties; and which produces a very fine spray with little or no overspray. Still another object is to make the shape of the spray envelope'adjustable from the outside by a simple axial adjustment of the oil tube passing through the burner.

To accomplish the foregoing general objects, and other more specific objects which will hereinafter appear, our invention resides in the oil burner elements and their relation one to another as are hereinafter more particularly described in the following specification. The specification is accompanied by drawings in which:

FIG. 1 is a longitudinal section through an oil burner embodying features of our invention;

FIG. 2 is a perspective view, drawn to larger scale, and

showing an atomizing assembly forming a part of the burner;

FIG. 3 is a rear view of the parts shown in FIG. 2;

FIG. 4 is a fragmentary section corresponding to the right end of FIG. 1, but drawn to larger scale and more completely sectioned;

FIG. 5 is a fragmentary view explanatory of one feature of the invention;

FIG. 6 is a fragmentary section explanatory of another feature of the invention;

' United States Patent O FIGS. 7 and 8 are fragmentary views showing the axial adjustability of the atomizing assembly relative to the atomizing air tube;

FIG. 9 is explanatory of the effect of such adjustment on the shape of the spray envelope; and

FIG. 10 is a longitudinal section like FIG. 1, but showing a combined oil and gas burner embodying features of the invention.

Referring to the drawing, and more particularly to FIG. 1, the oil burner there shown comprises an oil tube 12, an atomizing air tube 14 around the oil tube 12, a combustion air tube 16 around the atomizing air tube 14, and an atomizing assembly generally designated 18 at the inner end of the burner. The oil supply is connected at the outer end 20 of the oil tube 12. The atomizing air supply is connected at 22, and the combustion air supply is connected at 24.

The atomizing air is low pressure air having a pressure of from say 16 to 24 ounces per square inch. The combustion air may be supplied at still lower pressure, say

3,254,846 Patented June 7, 1966 four ounces per square inch. However, if desired the combustion air may be supplied at the same pressure as th atomizing air, say 16 to 24 ounces per square inch, in which case a single source or blower may be employed for both the atomizing air and the combustion air. These and other. numerical values given herein are given by way of example, and are not intended to limit the scope of the invention.

Referring now to FIG. 4, the atomizing assembly 18 includes an oil spray tip 26 at the end of the oil tube 12. This blocks the oil tube against axial flow, but has a plurality of oil spray holes 28 disposed transversely of the axis of the burner. In simplest form the holes 28'are radial, and in the particular case here shown there are eight such holes. A shallow peripheral groove 30 preferably is formed at the ends of the holes 28 for better distribution of oil all around the tip. In the present case the groove is formed by an annular inward step at 30 in the diameter of the tip 26.

The assembly 18 further includes an atomizing air divider sleeve 32 around the tip 26. The divider 32 may be said to divide the atomizing air into primary atomizing air which flows inside the sleeve 32, and secondary atomizing air which flows outside the sleeve 32. The inner surface of the sleeve 32 is so shaped as to greatly increase the air flow velocity at the oil spray holes 28. For this purpose the inner surface is convergent at 34 (FIG. 5). It is divergent at 36 around the tip 26, but at this point the tip 26 is itself more sharply divergent, and the net effect is to substantially maintain if not to increase the high air velocity.

Referring now to FIG. 6, the oil flowing through spray hole 28 discharges oil across the air path, and the high velocity air indicated at 38 atomizes and carries the oil with it. At high oil flow rates the oil impinges against the inner surface of the sleeve 32, as shown at 36, which helps further break up and atomize the oil. Air is flowing outside the divider sleeve 32, and the latter preferably terminates in a relatively sharp edge 40, which helps atomize the oil. The oil tip 26 itself has a sharp edge at 42, and at the outer edge of the step 30. These edges also help atomize the oil. The step 30 shields the emerging oil at the holes enough to facilitate spread of oil around the tip between the holes, and thus makes for better distribution of the'oil, and more etficient atomization of the same. Finally there is the action of the stream of secondary atomizing air on the expanding stream of oil laden primary atomizing air.

Reverting to FIGS. 3 and 4, the rear portion of the tip 26 is centered by means of vanes 44. In the present case there are five vanes, and these are disposed helically between the rear or cylindrical portion 46 of the oil spray tip, and the air divider sleeve 32. The vanes 44 act as spin vanes which impart a spiral motion to the air, as shown by the arrows in FIG. 5. This helps expand the air stream outwardly in addition to the effect of the divergent path itself.

Reverting now to FIGS. 2, 3 and 4, the air divider sleeve 32 is centered by radial vanes 48. In the present case there are five such vanes, and they are disposed axially. In this case it is preferred not to spin the air, and instead it is desired that the air move forward and even inward somewhat, so as to help promptly meet and mix with the oil at edge 40, and to help efiiciently atomize the same. This is shown by the arrows in FIGS. 7 and 8 of the drawing.

The effective working part of the oil spray tip26 (FIG. 4) is the divergent part. The cylindrical part 46 is mainly for convenience of attachment and centering. The vanes 44 and 48 are preferably located at the rear portion of the oil spray assembly, that is, around the cylindrical part 46, and behind the divergent part of the'tip, so that the collateral air streams separated by the vanes have an opportunity to return or coalesce into a single annular stream before reaching the oil.

The inner end of the atomizing air tube preferably has an annular convergent lip 50. Instead of altering the tube 14, the lip 50 may be formed on a cylinder 52, which is secured to the inner end of the tube 14, as by welding. The part 52 is not welded to the centering vanes 48, which preferably fit slidably Within the part 52, so that one may be moved axially relative to the other.

In FIG. 7 the secondary atomizing air flows through convergent nozzle 50 so that maximum velocity is obtained at the edge 40. The secondary atomizing air stream is directed axially or straight forward, and strikes the oil laden primary atomizing air stream, which is traveling in an expanding helical stream. This results in shearing forces on the atomized oil particles, which causes them to be broken into smaller particles. If the two air streams were directed forward along the same axis very little additional atomization would take place.

Referring now to FIG. 1, the oil tube 12 is preferably axially adjustable relative to the remainder of the burner. For this purpose it passes through an O ring held by a part 54 secured to and supported by the end 56. The adjustment is locked by a set screw 58. No specific adjusting means is here shown, but it will be understood that if desired, an appropriate screw adjustment or other such means may be provided.

Comparing FIGS. 7 and 8, the oil spray assembly is shown in relatively forward position in FIG. 7, and in relatively retracted position in FIG. 8. As indicated by the arrows, the convergent lip 50 is more effective in narrowing the air stream when the tip assembly is retracted, as shown in FIG. 8. The net effect of this may be explained with reference to FIG. 9, in which the solid lines 54 represent the spray envelope when the spray assembly is in the forward position shown in FIG. 7, and the broken lines 56 represent the narrowed spray envelope produced when the spray tip is in the retracted position shown in FIG. 8.

If desired the combustion air may be given a spin, and referring to FIGS. 1 and 4, additional vanes 90 may be added for this purpose. In a typical case, there are say four or six such vanes, most simply made of sheet metal, and anchored in the secondary air tube 16 as by means of threaded studs 92 and nuts 94. The angular position of the vanes may be adjusted from the outside, and the adjustment is locked when the nuts are tightened. These spin vanes constitute an additional means to assist in changing the shape of the flame, because increased spin causes a shorter bushier flame. With the vanes axially directed the flame is lengthened. The use of these vanes is optional.

For convenience the vanes may be referred to as being helical, but this term is employed in an approximate sense, as applied to any angularly disposed vane which produces a spin, and is not intended to mean that the vane is truly helical, for it may have a simple flat or plane surface.

It was previously mentioned that the cast vanes 48 for the secondary atomizing air are axially directed in the particular burner here illustrated. However, these vanes 48 also may be disposed at an angle in order to impart a spin to the secondary atomizing air. In such case the spin is preferably in a direction opposite to that caused by the vanes 44 for the primary atomizing air. The resulting reverse spin causes increased shearing action on the oil particles. If the vanes 48 are inclined in the same direction as the vanes 44 the shearing action is reduced. This is a possible construction if it be desired to lengthen out the spray pattern. In the case of vanes 44- and 48, as in the case of vanes 90, the term helical is used in an approximate rather than an exact sense, and applies to any angularly disposed vane which causes spin.

An air pressure of sixteen to twenty-four ounces per square inch Was mentioned for the atomizing air. A

. of oil between the oil holes.

The air passage leading to the oil holes is defined by surfaces so contoured that the passage is generally convergent in cross sectional area. This increases the velocity of the air approaching the oil spray holes. The convergent part increases air velocity, and the divergent part substantially maintains the increased air velocity.

In review, it will be seen that the present oil burner comprises a long oil tube 12, a long atomizing air tube 14 around the oil tube 12, along combustion air tube 16 around the atomizing air tube 14, and a very short atomizing assembly 18 localized at the inner end of the burner. This assembly 18 includes an oil spray tip 26 (FIG. 4) at the inner end of the oil tube 12, the said tip having a plurality 'of oil spray holes 28 disposed transversely of the axis of the burner, and it further includes an atomizing air divider sleeve 32 around the tip 26 between the tip and the atomizing air tube. This divider sleeve 32 has a short axial length and is fully open at its rear end around the oil tube. The spray tip and the divider sleeve and the atomizing air tube and the combustion air tube are all-one within another at the inner end of the burner.

Both ends of the divider sleeve 32 have relatively sharp edges. The sharp entrant edge serves to divide the atomizing air with minimum turbulence. The sharp terminal edge serves to assist in atomization of the oil. For the same purpose of assisting atomization of the oil, the spray tip also terminates in relatively sharp edges. The inner surface of the divider sleeve is convergent behind the tip and is divergent at the tip. The outer surface of the top is itself even more divergent than the sleeve, and more so than is shown in the drawing, thereby adding to the increased velocity produced by the convergent part of the divider sleeve. The sharp end edges of the sleeve facilitate the provision of the convergent and divergent inner surfaces of the sleeve, a section through the sleeve being triangular, as will be seen in the drawing. The oil spray assembly 18, including the spray tip 26 and the divider sleeve 32, is adjustable in axial direction relative to the atomizing air tube 14 and its inner end 50, in order to vary the width of the spray, as suggested in FIGS. 7, 8, and 9.

In manufacturing the burner the spray tip 26, 46 (FIG. 4) may be cast integrally with the spin vanes 44. The air divider sleeve 32 may be cast integrally with its centering vanes 48. These parts may be secured to the inner end of the oil tube 12 in any desired manner, as by a screw fit. The centering vanes 48 are left free and slidable within the cylindrical part 52 at the end of the atomizing air tube 14. The tip portion with the radial holes 28 may be made separately and screwed into the main cast body as shown at 27. These parts are preferably' made of stainless steel.

The remainder of the burner may-be made largely of separate parts which are assembled by welding, as indicated in the drawing. For example, the flange rings and 62 in FIG. 1 are welded to the parts 25 and 16 respectively. The same applies to the flange 64, which may be welded to the pipe connection 24. The manufacturing procedure used is merely a matter of convenience, and would depend on the quantity of burners being made in a particular size. More casting may be used for large quantity manufacture. In large sizes of burner, welding has the advantage of lighter weight.

In small size the present burner may handle, say fifty gallonsper hour with a turndown to one tenth, thus handling a range of from say five to fifty gallons per hour. In large size the burner may handle, say five hundred gallons per hour, with a turndown to about one tenth, thus handling a range of from say fifty to five hundred gallons per hour.

A burner embodying the features here described may, when necessary, be used in a combination oil and gas burner. In some locations gas is less expensive than oil when gas is available, but is only available intermittently, and therefore a combination burner is desired. Such a burner is shown in FIG. 10, and it again comprises an oil tube 12' within an atomizing air tube 14' within a combustion air tube 16', and an oil spray assembly 18 is disposed at the inner ends of the tubes 12 and 14, all as previously described.

However, in the present case there is an additional gas tube 70 located between the atomizing air tube 14' and the combustion air tube 16. A connection 72 leads into the gas tube 70, the gas flowing in the space between the tubes 14' and 70. In the particular structure shown the atomizing air is connected at 74, and this is sealed from the gas passage by an appropriate barrier 76. If desired, a ring of holes may be provided, one of which is indicated at 78, for the admission of a limited amount of the combustion-air into the gas flow tube. This premixing results in faster burning of the fuel, and helps obtain a clear or blue flame type of combustion. The amount of air admitted in this fashion may be regulated by the provision of a ring 80 having holes 82. The ring 80 may be moved through a small angle to bring the holes 82 into or out of registration with the holes 78. A screw which is accessible outside the burner may be used for this adjustment.

It is believed that the construction and operation of our improved oil burner, as well as the advantages thereof, will be apparent from the foregoing detailed description. It will also be apparent that while we have shown and described our invention in a preferred form, changes may be made in the structure shown, without departing from the scope of the invention as sought to be defined in the following claims. In the claims the reference to helical vanes is intended to include angularly disposed vanes which cause spin, even though the vanes may be straight or plane instead of truly helical.

We claim:

1. An industrial type oil burner of large capacity requiring only low pressure air, said burner comprising a long oil tube, a long atomizing air tube around the oil tube, a long combustion air tube around the atomizing air tube, both said air tubes being used simultaneously and a short atomizing assembly localized at the inner end of the burner, said assembly including an oil spray tip at the inner end of the oil tube and having a plurality of oil spray holes disposed transversely of the axis of the burner at the inner end of the assembly, and an atomizing air divider sleeve means around the tip between the tip and the atomizing air tube, the inner end of the atomizing air tube having an annular convergent lip, the inner end of the combustion air tube having an annular convergent lip, the divider sleeve means having a short axial length and being fully open at its rear end around the oil tube, the spray tip and the divider sleeve and the atomizing air tube and the combustion air tube all being one within another at the inner end of the burner, the inner surface of the divider sleeve means being shaped relatively to the outer surface of the spray tip to provide therebetween across-sectional flow area which generally decreases in the direction of flow so as to generally increase the air velocity therein approaching the oil spray holes, said divider sleeve means and said oil spray tip terminating in relatively sharp edges to assist in atomization of the oil, the atomizing assembly including the divider sleeve, and the inner end of the atomizing air 6 tube being relatively movable in axial direction to vary the width of the spray.

2. An industrial type oil burner, of larger capacity requiring only low pressure air, said burner comprising a long oil tube, a long atomizing air tube-around the oil tube, a long combustion air tube around the atomizing air tube, both said air tubes being used simultaneously, and a short atomizing assembly localized at the inner end of the burner, said assembly including an oil spray tip at the inner end of the oil tube and having a plurality of oil spray holes disposed transversely of the axis of the burner at the inner end of the assembly, and an atomizing air divider sleeve means around the tip between the tip and the atomizing air tube, the divider sleeve means having a short axial length and being fully open at its rear end around the oil tube, the spray tip and the divider sleeve and the atomizing air tube and the combustion air tube all being one within another at the inner end of the burner, helically disposed vanes between the tip and the dividersleeve, axial vanes between the divider sleeve and the atomizing air tube, the inner surface of the divider sleeve means being shaped relatively to the outer surface of the spray tip to provide therebetween a crosssectional flow area which generally decreases in the direction of flow so as to generally increase the air velocity therein approaching the oil spray holes, said divider sleeve means and said oil spray tip terminating in relatively sharp edges to assist in atomization of the oil.

' 3. An industrial type oil burner of large capacity requiring only low pressure air, said burner comprising a long oil tube, a long atomizing air tube around the oil tube, a long combustion air tube around the atomizing air tube, both said air tubes being used simultaneously, and a short atomizing assembly localized at the inner end of the burner, said assembly including an oil spray tip at the inner end of the oil tube and having a plurality of oil spray holes disposed transversely of the axis of the burner at the inner end of the assembly, and an atomizing air divider sleeve means around the tip bet-ween the tip and the atomizing air tube, the inner end of the atomizing air tube having an annular convergent lip, the inner end of the combustion air tube having an annular convergent lip, the divider sleeve means having a short axial length and being fully open at its rear end around the oil tube, the spray tip and the divider sleeve and the atomizing air tube and the combustion air tube all being one within another at the inner end of the burner,- helically disposed vanes between the tip and the divider sleeve, axial vanes between the divider sleeve and the atomizing air tube, the inner surface of the divider sleeve means being shaped relatively to the outer surface of the spray tip to provide ere/between a cross-sectional flow area which generally decreases in the direction of flow so as to generally increase the air velocity therein approaching the oil spray holes, said divider sleeve means and said oil spray tip terminating in relatively sharp edges to assist in atomization of the oil, the atomizing assembly including the divider sleeve, and the inner end of the atomizing air tube being relatively movable in axial direction to vary the Width of the spray.

4. An industrial type oil burner of large capacity requiring only low pressure air, said burner comprising a long =oil tube, a long atomizing air tube around the oil tube, a long combustion air tube around the atomizing air tube, both said air tubes being used simultaneously, and a short atomizing assembly localized at the inner end of the burner, said assembly including an oil spray tip at the inner end of the oil tube and having a plurality of oil spray holes disposed transversely of the axis of the burner at the inner end of the assembly, a peripheral step at the ends of said spray holes for better distribution of oil around the tip, and an atomizing air divider sleeve means around the tip between the tip and the atomizing air tube, the divider sleeve means having a short axial length and being fully open at its rear end around 4 the oil tube, the spray tip and the divider sleeve and the atomizing air tube and the combustion air tube all being one within another at the inner end of the burner, helic-ally disposed vanes between the tip and the divider sleeve, axial vanes between the divider sleeve and the atomizing air tube, the inner surface of the divider sleeve means being shaped relatively to the outer surface of the spray tip to provide therebetween a cross-sectional flow area which generally decreases in the direction of flow so as to generally increase the air velocity therein approaching the oil spray holes, the oil spray tip terminating in a relatively sharp edge to help atomize the oil, both ends of said divider sleeve having relatively sharp edges, the sharp entrant edge serving to divide the atomizing air with minimum turbulence, and the sharp terminal edge assisting in the atomization of the oil.

5'. An industrial type oil burner of large capacity requiring only low pressure air, said burner comprising a long oil tube, a long atomizing air tube around the oil tube, a long combustion air tube around the atomizing air tube, both said air tubes being used simultaneously, and a short atomizing assembly localized at the inner end of the burner, said assembly including an oil spray tip at the inner end of the oil tube and having a plurality of oil spray holes disposed transversely of the axis of the burner at the inner end of the assembly, a peripheral step at the ends of said oil spray holes for better distribution of oil around the tip, and an atomizing air divider sleeve means around the tip between the tip and the atomizing air tube, the inner end of the atomizing air tube having an annular convergent lip, the inner end of the combustion air tube having an annular convergent lip, the divider sleeve means having a short axial length and being fully open at its rear end around the oil tube, the spray tip and the divider sleeve and the atomizing air tube and the combustion air tube all being one within another at the inner end of the burner, helically disposed vanes be tween the tip and the divider sleeve, axial vanes between the divider sleeve and the atomizing air tube, the inner surface of the divider sleeve means being shaped relatively to the outer surface of the spray tip to provide therebetween a cross-sectional flow area which generally decreases in the direction of flow so as to generally increase the air velocity therein approaching the oil spray holes, both ends of said divider sleeve having relatively sharp edges, the sharp entrant edge serving to divide the atomizing air with minimum turbulence, and the sharp terminal edge assisting in the atomization of the oil, the atomizing assembly including the divider sleeve, and the inner end of the atomizing air tube being relatively movable in axial direction to vary the width of the spray.

6. An industrial type oil burner of large capacity requiring only low pressure air, said burner comprising a long oil tube, a long atomizing air tube around the oil tube, a long combustion air tube around the atomizing air tube, both said air tubes being used simultaneously, and a short atomizing assembly localized at the inner end of the burner, said assembly including an oil spray tip at the inner end of the oil tube and having a plurality of oil spray holes disposed transversely of the axis of the burner at the inner end of the assembly, and an atomizing 'air divider sleeve around the tip between the tip and the atomizing air tube, the divider sleeve having a short axial length and being fully open at its rear end around the oil tube, the spray tip and the divider sleeve and the atomizing air tube and the combustion air tube all being one within another at the inner end of the burner, the outer surface of the tip being divergent, the divider sleeve being non-uniform in thickness, the inner surface of the divider sleeve being divergent at the tip and convergent behind the tip to increase the velocity of the air therein before reaching the oil spray holes, the oil spray tip terminating in a relatively sharp edge to help atomize the oil, both ends of said divider sleeve having relatively sharp edges, the sharp entrant edge serving to divide the atomizing air with minimum turbulence, the sharp terminal edge assisting in the atomization of the oil, and both of said sharp edges facilitating the provision of the aforesaid convergent and divergent inner surfaces.

'7. An industrial type oil burner of large capacity requiring only low pressure air, said burner comprising a long oil tube, a long atomizing air tube around the oil tube, a long combustion air tube around the atomizing air tube, both said air tubes being used simultaneously, and a short atomizing assembly localized at the inner end of the burner, said assembly including an oil spray tip at the inner end of the oil tube and having a plurality of oil spray holes disposed transversely of the axis of the burner at the inner end of the assembly, and an atomizing air divider sleeve around the tip between the tip and the atomizing air tube, the divider sleeve having a short axial length and being [fully open at its rear end around the oil tube, the spray tip and the divider sleeve and the atomizing air tube and the combustion air tube all being one within another at the inner end of the burner, the outer surface of the tip being divergent, the divider sleeve being nonuniform in thickness, the inner surface of the divider sleeve being divergent at the tip and convergent behind the tip to increase the velocity of the air therein before reaching the oil spray holes, the oil spray tip terminating in a relatively sharp edge to help atomize the oil, both ends of said divider sleeve having relatively sharp edges, the sharp entrant edge serving to divide the atomizing air with minimum turbulence, the sharp terminal edge assisting in the atomization of the oil, and both of said sharp edges facilitating the provision of the aforesaid convergent and divergent inner surfaces, the atomizing assembly being moveable in axial direction relative to the inner end of the atomizing air tube to vary the width of the spray.

8. An industrial type oil burner of large capacity requiring only low pressure air, said burner comprising a long oil tube, a long atomizing air tube around the oil tube, a long combustion air tube around the atomizing air tube, both said air tubes being used simultaneously, and a short atomizing assembly localized at the inner end of the burner, said assembly including an oil spray tip at the inner end of the oil tube and having a plurality of oil spray holes disposed transversely of the axis of the burner at the inner end of the assembly, and an atomizing air divider sleeve around the tip between the tip and the atomizing air tube, the divider sleeve having a short axial length and being fully open at its rear end around the oil tube, the spray tip and the divider sleeve and the atomizing air tube and the combustion air tube all being one within another at the inner end of the burner, helically disposed vanes between the tip and the divider sleeve, axial vanes between the divider sleeve and the atomizing air tube, the outer surface of the tip being divergent, the divider sleeve being non-uniform in thickness, the inner surface of the divider sleeve being divergent at the tip and convergent behind the tip to increase the velocity of the air therein before reaching the oil spray holes, the oil spray tip terminating in a relatively sharp edge to help atomize the oil, both ends of said divider sleeve having relatively sharp edges, the sharp entrant edge serving to divide the atomizing air with minimum turbulence, the sharp terminal edge assisting in the atomization of the oil, and both of said sharp edges'facilitating the provision of the aforesaid convergent and divergent inner surfaces.

9. An industrial type oil burner of large capacity requiring only low pressure air, said burner comprising a long oil tube, a long atomizing air tube around the oil tube, a long combustion air tube around the atomizing air tube, both said air tubes being used simultaneously, and a short atomizing assembly localized at the inner end of the burner, said assembly including an oil spray tip at the inner end of the oil tube and having a plurality of oil spray holes disposed transversely of the axis of the burner at the inner end of the assembly, said spray tip having a shallow peripheral step at the ends of said oil spray holes for better distribution of oil around the tip, and an atomizing air divider sleeve around the tip between the tip and the atomizing air tube, the divider sleeve having a short axial length and being fully open at its rear end around the oil tube, the spray tip and the divider sleeve and the atoniizing air tube and the combustion air tube all being one within another at the inner end of the burner, the outer surface of the tip being divergent, the divider sleeve being non-uniform in thickness, the inner surface of the divider sleeve being divergent at the tip and convergent behind the tip to increase the velocity of the air therein before reaching the oil spray holes, the oil spray tip terminating in a relatively sharp edge to help a-tomize the oil, both ends of said divider sleeve having relatively sharp edges, the sharp entrant edge serving to divide the atomizing air with minimum turbulence, the sharp terminal edge assisting in the atomization of the oil, and both of said sharp edges facilitating the provision of the aforesaid convergent and divergent inner surfaces.

10. An oil burner requiring only low pressure air, said burner comprising along oil tube, a long atomizing air tube around the oil tube, a long combustion air tube around the atoniizing air tube, and a short atomizing assembly localized at the inner end of the burner, said assembly including an oil spray tip at the inner end of the oil tube and having a plurality of oil spray holes dis- (posed transversely of the axis of the burner at the inner end of the assembly, a shallow peripheral groove at the ends of said oil spray holes for better distribution of oil around the tip, an atomizing air divider sleeve around the tip between the tip and the atomizing air tube, the divider sleeve having a short axial length and being fully open at its rear end around the oil tube, the spray tip and the divider sleeve and the atomizing air tube and the coinbustion air tube all being one within another at the inner end of the burner, 'helically disposed vanes between the tip and the divider sleeve, axial vane-s between the divider sleeve and the atomizing air tube, the outer surface of the tip being divergent, the divider sleeve being non-uniform in thickness, the inner surface of the divider sleeve being divergent at the tip and convergent behind the tip to increase the velocity of the air therein before reaching the oil spray holes, both ends of said divider sleeve having relatively sharp edges, the sharp entrant edge serving to divide the atomizing air with minimum turbulence, the sharp terminal edge assisting in the atomization of the oil, and both of said shanp edges faclitating the provision of the aforesaid convergent and divergent inner surfaces, the oil spray assembly being movable in axial direction relative to the inner end of the atomizing air tube to vary the width of the spray.

References Cited by the Examiner UNITEDSTATES PATENTS 1,640,728 8/1927 Scott 158-76 X 1,702,339 2/1929 Pukuhara 158736 1,740,296 12/1929 Gerdes et al. 15876 2,368,178 1/1945 Turpin 158'11 2,526,220 10/1950 Goddard 1581.5 X 2,746,531 5/1956 Brelsford 158-76 3,049,173 8/1962 Costello et a1 15811 X FREDERICK L. MATTESON, .TR., Primary Examiner.

E. G. FAVORS, Assistant Examiner. 

1. AN INDUSTRIAL TYPE OIL BURNER OF LARGE CAPACITY REQUIRING ONLY LOW PRESSURE AIR, SAID BURNER COMPRISING A LONG OIL TUBE, A LONG ATOMIZING AIR TUBE AROUND THE OIL TUBE, A LONG COMBUSTION AIR TUBE AROUND THE ATOMIZING AIR TUBE, BOTH SAID AIR TUBES BEING USED SIMULTANEOUSLY AND A SHORT ATOMIZING ASSEMBLY LOCALIZED AT THE INNER END OF THE BURNER, SAID ASSEMBLY INCLUDING AN OIL SPRAY TIP AT THE INNER END OF THE OIL TUBE AND HAVING A PLURALITY OF OIL SPRAY HOLES DISPOSED TRANSVERSELY OF THE AXIS OF THE BURNER AT THE INNER END OF THE ASSEMBLY, AND AN ATOMIZING AIR DIVIDER SLEEVE MEANS AROUND THE TIP BETWEEN THE TIP AND ATOMIZING AIR TUBE, THE INNER END OF THE ATOMIZING AIR TUBE HAVINGG AN ANNULAR CONVERGENT LIP, THE INNER END OF THE COMBUSTION AIR TUBE HAVING AN ANNULAR CONVERGENT LIP, THE DIVIDER SLEEVE MEANS HAVING A SHORT AXIAL LENGTH AND BEING FULLY OPEN AT ITS REAR END AROUND THE OIL TUBE, THE SPRAY TIP AND THE DIVIDER SLEEVE AND THE ATOMIZING AIR TUBE AND THE COMBUSTION AIR TUBE ALL BEING ONE WITHIN ANOTHER AT THE INNER END OF THE BURNER, THE INNER SURFACE OF THE DIVIDER SLEEVE MEANS BEING SHAPED RELATIVELY TO THE OUTER SURFACE OF THE SPRAY LIP TO PROVIDE THEREBETWEEN A CROSS-SECTION FLOW AREA WHICH GENERALLY DECREASES IN THE DIRECTION OF FLOW SO AS TO GENERALLY INCREASE THE AIR VELOCITY THEREIN APPROACHING THE OIL SPRAY HOLES, SAID DIVIDER SLEEVE MEANS AND SAID OIL SPRAY TIP TERMINATING IN RELATIVELY SHARP EDGES TO ASSIST IN ATOMIZATION OF THE OIL, THE ATOMIZING ASSEMBLY INCLUDING THE DIVIDER SLEEVE, AND THE INNER END OF THE ATOMIZING AIR TUBE BEING RELATIVELY MOVABLE IN AXIAL DIRECTION TO VARY THE WIDTH OF THE SPRAY. 